Recent advances in ensemble density functional theory and linear response theory for strong correlation

The formulations and performances of spin-restricted ensemble-referenced KS and mixed-reference spin-flip time-dependent density functional theory incorporating strong correlations into density functional theories are documented. As a result of balanced dynamic and nondynamic correlation, they are capable of describing strongly correlated challenging systems including diradicals, bond dissociation, conical intersections, doubly excited states, and so on, overcoming the limitations of current density functional theories.